Proximity Services (ProSe) are services that can be provided by the 3GPP system based on UEs being in proximity to each other. One of these services is ProSe Discovery. The ProSe service is described in 3GPP TS 22.278 and 3GPP TS 23.303 and it allows the possibility of Device-to-Device (D2D) communication, without passing messages through the Radio Access Network.
ProSe Discovery identifies that ProSe-enabled UEs are in proximity of each other, using evolved UMTS Terrestrial Radio Access (E-UTRA), whether or not they are using the evolved UMTS Terrestrial Radio Access Network (E-UTRAN) or the Extended Packet Core (EPC) network, when permission, authorization and proximity criteria are fulfilled. The proximity criteria can be configured by the operator.
The ProSe Discovery process involves a discovery message being sent over an air interface by one device, and received by another. The other device then responds with a discovery message. Both discovery messages comprise a ProSe code for identifying each of the devices. However, one device may replay the ProSe code received from the other device and so pretend to be said other device. Therefore, there is a need for devices to securely discover one another as they are in proximity of each other.